(1) Field of the Invention
The present invention relates to a cylinder head cooling structure of an overhead valve engine, such as an industrial engine.
(2) Description of Related Art
For example, an air-cooled V-type engine described below is known as an overhead valve industrial engine.
In such an air-cooled V-type engine, an oil inlet is provided in the bottom of a pushrod chamber in a downstream cylinder unit located downstream in a cam rotation direction relative to a rib, and the oil inlet faces the cam and communicates with the inside of a head cover of the downstream cylinder unit through the pushrod chamber of the downstream cylinder unit.
As such, oil mist in a crankcase condenses on the ceiling of the crankcase, and condensed oil drops from the rib, splashes over the oil inlet by the cam, and is supplied to the head cover of the downstream cylinder unit by blow-by gas rising through the pushrod chamber.
That is, a conventional overhead valve (OHV) engine is configured such that engine oil is supplied into a cylinder head through the pushrod chamber by oil mist produced by stirring oil as a crankshaft etc. is rotated in the crankcase and by natural diffusion of the oil mist due to rotation of a camshaft.
However, it has been found that cooling capacity tends to be insufficient depending on various conditions, such as engine structure, usage status and use environment, for example, in such a manner that an engine arrangement may cause uneven cooling or the engine is continuously operated in a high temperature location. One of eminent failures is that a stem seal of a valve on the exhaust side (i.e., an exhaust valve) under severe temperature conditions is susceptible to degradation by heat.